1. Field of the Invention
The present invention relates to a flow adjusting valve that is employed in a fluid transfer pipe used in various industrial fields, for example, chemical plants, semiconductor manufacturing, biotechnology, and so on, and that controls the flow of liquid fluid.
2. Description of Related Art
Known flow adjusting valves in the related art that adjust the flow of liquid, such as chemicals, etc., include those that employ a needle valve, as disclosed in Japanese Unexamined Patent Application, Publication No. 2006-153262. With such flow adjusting valves, remote control of the degree of opening of the needle valve has also been implemented by providing a stepper motor that rotationally drives a shaft piece and a conversion mechanism that converts the rotation of the shaft piece to forward/backward movement of the shaft piece.
In addition, conventional flow adjusting valves include those in which an open/close valve that performs fully-opening/fully-closing operation serves as a main component and that is provided with an electrically powered flow adjusting function. With the open/close valves having such a flow adjusting function, it has been pointed out that precision of the flow adjustment itself deteriorates, that there is a problem with flow reproducibility due to changes in a valve seat shape, and that there is a problem with durability and strength because the motor is subjected to a piston load.
With the flow adjusting valves employing a needle valve, in order to maintain accurate flow adjustment, it is desirable to avoid the fully-closed operation, in which a needle valve is in close contact with a valve seat. That is, when the needle valve is in close contact with the valve seat, the shape of the valve orifice is deformed due to drag, friction, etc.; therefore, the original orifice shape (dimensions) cannot be maintained, and, as a result, accurate flow adjustment in accordance with the degree of opening (orifice shape) of the needle valve becomes difficult, causing the problem of the flow reproducibility.
Accordingly, when installing a flow adjusting valve in a fluid transfer pipe, an open/close valve (also referred to as a “shutoff valve”) is normally installed in series with the flow adjusting valve, and this open/close valve is fully closed to perform the fully-closed operation to block fluid flow. The needle valve is not fully closed in this case, and a minimum necessary degree of opening for ensuring enough space so that the needle valve does not come in contact with the valve seat is set as the minimum degree of opening.
Note that, in the case in which the flow adjusting valve adjusts the flow by changing the degree of opening of the needle valve, the open/close valve is maintained in a fully-open state.
However, when the flow adjusting valve and the open/close valve are installed in series, particularly when the open/close valve is connected next to the flow adjusting valve in a lateral series in a horizontal pipe, the footprints of the valves themselves, that is, spaces required for installing the valves, become large. Therefore, size reduction of the apparatus as a whole is prevented.
Against such a background, there is a demand for a flow adjusting valve that has a flow adjustment function and a flow-path blocking function that fully closes a flow path. That is, there is a demand for reducing an installation space by implementing the flow-path blocking function in a flow adjusting valve employing a needle valve, without losing the flow reproducibility.